Frequency hopping sequence generator

ABSTRACT

A frequency hopping sequence generator using a single binary sequence generator adopted for a multi-group frequency hopping frequency division multiple access (FH-FDMA) communication system, includes one binary sequence generator for generating consecutive binary sequences, and plural non-binary sequence converter for mapping a binary sequence into an independent non-binary sequence in each group by using a group ID.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a frequency hopping sequencegenerator and, more particularly, to a frequency hopping sequencegenerator using a single binary sequence generator adopted for amulti-group frequency hopping frequency division multiple access(FH-FDMA) communication system

[0003] 2. Description of the Background Art

[0004] The multi-group FH-FDMA is a frequency-hopping spread spectrum(FHSS) communication system exerting an excellent performance in athreatening environment such as jamming, wire-tapping, frequencyselection fading, a position detection or the like.

[0005] The characteristics of the frequency hopping sequence generatorrequired for the multi-group FH-FDMA communication system arefacilitation of a key management, auto-correlation of frequency hoppingsequence assigned to each group, and orthogonality (non-collision ofchip) between groups or independence.

[0006] Let q denote the number of frequency slots in a FHSS system andlet f_(i) denote the center frequency of the i-th slot, 0≦i≦q−1. Thecenter frequencies are usually chosen that the slots be spaced uniformlyacross the frequency band allotted to the system. A FH pattern is asequence x=(x₀, x₁, . . . , X_(N−1)) of N elements from the set f₀,f_(i), . . . , f_(q−1) specifying the order in which the slots are to beused by a particular transmitter. However, it is not necessary that theelements of the set be the center frequencies of the slots. All thevarious properties of hopping patterns can be described provided onlythat the set contains q distinct elements. In short, one can also regarda hopping pattern as a sequence of elements, and the pattern can alwaysbe transformed into a sequences of frequencies by a suitable one to onemapping from this set to f₀, f_(i), . . . , f_(q−1). This is theviewpoint that will be taken in the rest of this document. Inparticular, hopping patterns will be viewed as sequences of elementsfrom the finite field q=2^(k).

[0007] In general, the frequency hopping sequence generator used in theFHSS system uses a non-binary sequence converter that maps binaryoutputs of a binary m-sequence generator into non-binary sequences, i.e.sequences of elements aforementioned.

[0008]FIG. 1 is a schematic block diagram of a frequency hoppingsequence generator consisting of a binary sequence generator 100 and anon-binary sequence converter 200 in accordance with a conventional art.

[0009] With reference to FIG. 1, the frequency hopping sequence isgenerated by the non-binary sequence converter 200 which, as mentionedabove, maps the consecutive binary outputs of the general binarysequence generator 100 into the non-binary sequences.

[0010] Since a periodic binary m-sequence of span-n characteristicsgenerates different 2^(n) tuples for one period when observingconsecutive n tuples, when read out k (k<n) tuples of the binarysequence continuously, the occurrence frequency of each of 2^(k) tuplesbecomes 2^(n−k). In this manner, consecutive k tuples of the binarysequence generator 100 can be simply converted into frequency hoppingsequences having 2^(k) symbols with an even occurrence frequency.

[0011]FIG. 2 shows an internal construction of the non-binary sequenceconverter 200 of FIG. 1, illustrating that a binary sequence is mappedinto a non-binary sequence when the number of frequency hopping slots isan exponent of 2.

[0012] With reference to FIG. 2, an exclusive-OR operator 230exclusive-ORs outputs of a shift register 210 and corresponding outputsof an offset data storing unit 220 to generate a non-binary sequence(Y₁, Y₂, . . . , Y_(v)). A set of different sequences generatedaccording to values stored in the offset data storing unit 220 can beused as a sequence set for a FH-CDMA.

[0013] However, when the conventional frequency hopping sequencegenerator is applied to the multi-group FH-FDMA communication system,the number of the frequency hopping sequence generator as shown in FIG.1 is required as many as groups, resulting in hardware complexity of thecommunication system. Also, since the number of keys is required as manyas groups, the keys should be managed as many as the groups, resultingin degraded facilitation of key management.

[0014] In addition, problems relating to the synchronization andorthogonality (chip non-collision) or independence between frequencyhopping sequence generators should be solved.

SUMMARY OF THE INVENTION

[0015] Therefore, an object of the present invention is to provide afrequency hopping sequence generator using a single binary sequencegenerator on the basis of a band splitting concept that an entirehopping band is divided as many as groups.

[0016] The key idea of the present invention is first to decompose theavailable hopping frequency slots of the hopping bandwidth into disjointsubsets such that the number of slots in each subset is same and thenumber of subsets is equal to the number of the groups. Then, in orderto assure perfect orthogonality between the groups, each hopping groupis assigned to one of the subsets in a way that never provides the samesubset for different groups, which is called “coarse addressing”mechanism. Conceptually, once a subset for a group is determined throughthe coarse addressing process, the specific frequency slots within thesubset for the users in the group are found out through the “fineaddressing” process in a conventional way that a k-tuple vector selectedfrom n-stages of an FSR generating an m-sequence is mapped to a hoppingslot as a reference address for the users in the group in FDMA format.

[0017] It is noteworthy that the fine addressing process in each subsetis performed independently on each other group, which make it impossibleto predict the frequency slot of one of the groups only from theinformation about the hopping slot of any other group at each hoppinginstance during the period for the higher robustness against hostileinterception and jamming.

[0018] Moreover in practice, since the two base addresses for the coarseaddressing and fine addressing are from the same PN generator becauseone PN generator is assumed in the developed theorem, the two processesin the proposed design are carried out concurrently, not sequentially.Therefore the hopping sequence generator based on the developed theoremsdoes not suffer latency that might be great concern in constructing FHpatterns for a fast frequency hopping system.

[0019] And it was proved that those resulting hopping sequences have thefavorable characteristics aforementioned.

[0020] To achieve these and other advantages, as embodied and broadlydescribed herein, there is provided a frequency hopping sequencegenerator applied for a multi-group FH-FDMA, including: one binarysequence generator for generating consecutive binary sequence; andplural non-binary sequence converter for mapping the binary sequenceinto an independent non-binary sequence in each group by using a groupID.

[0021] The non-binary sequence converter includes: a shift registerblock for receiving a binary sequence; a group ID data storing unit forconverting the group ID into binary data; a divided band selector fordividing a hopping band as many as groups and allocating the groups toeach divided band; and a detailed hopping binary sequence selector foroutputting a value for generation of a detailed hopping sequence in eachdivided band.

[0022] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0024] In the drawings:

[0025]FIG. 1 is a schematic block diagram showing a general frequencyhopping sequence generator;

[0026]FIG. 2 is a view showing a conventional non-binary sequenceconverter;

[0027]FIG. 3 is an exemplary view showing a frequency hopping sequencegenerator used for a multi-group FH-FDMA in accordance with the presentinvention;

[0028]FIG. 4 shows a construction of a non-binary sequence converter inaccordance with the present invention;

[0029]FIG. 5 shows an internal construction of a divided band selector;and

[0030]FIG. 6 shows an internal construction of a detailed hopping binarysequence selector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0032]FIG. 3 is an exemplary view showing a frequency hopping sequencegenerator used for a multi-group FH-FDMA in accordance with the presentinvention.

[0033] As shown in FIG. 3, in a multi-group FH-FDMA communicationsystem, one binary sequence generator 100 and non-binary sequenceconverters 300 as many as N groups are used, instead using the frequencyhopping sequence generators of FIG. 1 as many as N groups.

[0034]FIG. 4 shows a construction of a non-binary sequence converter inaccordance with the present invention.

[0035] The non-binary sequence converter 300 includes a shift registerblock 310, a group ID data storing unit 320, a divided band selector330, a detailed hopping binary sequence selector 340, an offset datastoring unit 350 and an exclusive-OR operator 360.

[0036] In FIG. 4, the desired number (q) of frequency hopping sequencesis 2^(t) (t is integer), and if the number (N) of group is 2^(b) (b isinteger, ID={0, 1, . . . , N−1}), the shift register block 310 storingconsecutive binary sequences received from the binary sequence generator100 selects b outputs (X₁˜X_(b)) and m(t−b+N−1) outputs(X_(i+1)˜X_(i+m)). The group IID data storing unit 320 outputs A₁˜A_(b)from the group ID (G).

[0037] The group ID (G) is determined by the following equation (1);$\begin{matrix}{{G = {\sum\limits_{i = 1}^{b}A_{i}}},2^{i - 1}} & (1)\end{matrix}$

[0038] Outputs (X₁˜X_(b)) of the shift register block 310 and outputs(A₁˜A_(b)) of the group ID data storing unit 320 are inputted to thedivided band selector 330. FIG. 5 shows an internal construction of adivided band selector.

[0039] As shown in FIG. 5, in the divided band selector 330, anexclusive-OR operator 331 exclusive-ORs the outputs (X₁˜X_(b)) of theshift register block 310 and outputs (A₁˜A_(b)) of the group ID datastoring unit 320 to output divided band select values (B₁˜B_(b)).

[0040] The B₁˜B_(b) outputted from the divided band selector 330 isexclusive-ORed with values (M₁˜M_(b)) stored in the offset data storingunit 350 in the exclusive-OR operator 360, and values (Y₁˜Y_(b))indicating a final divided band are outputted.

[0041] As afore-mentioned, in order to generate a frequency hoppingsequence allocated to each group, some of the outputs of the binarysequence generator 100 and the group ID are exclusive-ORed in thedivided band selector 330. Since the result of the exclusive-ORoperation is a 1:1 bijection of mapping outputs (A₁˜A_(b)) into outputs(B₁˜B_(b)) for selection of divided band, an orthogonality betweengroups, that is, a non-collision, can be guaranteed.

[0042] For example, if there are four groups of G=0, 1, 2 and 3, a groupID “0”(A₂A₁)=00, group ID “1”(A₂A₁)=01, group ID “1(A₂A₁)=10, group ID“2”(A₂A₁)=11 according to equation (1). Assuming that output value(X₂X₁) of the binary sequence generator 100 is 01, outputs values (B₁B₂)of the divided band selector 330 corresponding to each group are 01, 00,11 and 10, respectively, so that different values are outputted eachgroup ID (that is, no collision occurs).

[0043] Outputs (X_(i+1)˜X_(i+m)) of the shift register block 310 andoutputs (A₁˜A_(b)) of the group ID data storing unit 320 are inputted tothe detailed hopping binary sequence selector 340.

[0044]FIG. 6 shows an internal construction of a detailed hopping binarysequence selector.

[0045] In FIG. 6, the binary sequence selector 340 includes a decoder341, plural AND gates 342 and OR gates 343.

[0046] The decoder 341 receives the outputs (A₁˜A_(b)) of the group IDdata storing unit 320 and outputs D₁˜D_(N). The outputs D₁˜D_(n) of thedecoder 341 and the outputs (X_(i+1)˜X_(i+m)) of the shift registerblock 310 are logically operated through the AND gate 342 and the ORgate 343. Accordingly, t−b outputs (B_(b+1)˜B_(t)) are selected from moutputs (X_(i+1)˜X_(i+m)) of the shift register block 310.

[0047] For example, on the assumption that the number (q) of thefrequency hopping sequences is 16, that is, t=4 and the number of groups(N)=4, and i=4 for convenience, m=t−b+N−1=4−2+4−1=5. Thus, B₃ and B₄ areselected for a detailed hopping each group ID in the divided band byusing five outputs (X₅˜X₉) of the shift register block 310. That is,values selected from five outputs values (X₅˜X₉) by the logicaloperation of the AND gate 342 and the OR gate 343 serving as a selectswitch are as follows:

[0048] If G=0, A₂A₁=00 and an output of the decoder 341 isD₁D₂D₃D₄=1000, so selected value (B₃,B₄)=X₅,X₆, and likewise,

[0049] If G=1, A₂A₁=01 D₁D₂D₃D₄=0100, (B₃,B₄)=X₆,X₇,

[0050] If G=2, A₂A₁=10 D₁D₂D₃D₄=0010, (B₃,B₄)=X₇,X₈,

[0051] If G=3, A₂A₁=11 D₁D₂D₃D₄=0001, (B₃,B₄)=X₈,X₉

[0052] Consequently, it is noted that a specific value is selected forgeneration of the detailed hopping sequence for each group ID.

[0053] B_(b+1)˜B₁ outputted from the detailed hopping binary sequenceselector 340 are exclusive-ORed with the values (M_(b+)1˜M₁) stored inthe offset data storing unit 350 by the exclusive-OR operator 360, and adetailed hopping sequence (Y_(b+)1˜Y₁) are outputted in the finaldivided band.

[0054] In the frequency hopping sequence (f), the upper Y₁˜Y_(b)indicates the N divided band, and the lower Y_(b+)1˜Y_(t) indicates thedetailed hopping sequences in the divided band. The frequency hoppingsequence (f) is determined by the below equation (2): $\begin{matrix}{f = {\sum\limits_{i = 1}^{l}{Y_{i}2^{i - 1}}}} & (2)\end{matrix}$

[0055] As described above, the frequency hopping sequence generator ofthe present invention has many advantages.

[0056] That is, for example, because the frequency hopping sequencegenerator uses the single binary sequence generator, a hardware size isreduced, and because only one key and group ID information are managed,it is easy to manage the key.

[0057] In addition, time synchronization between groups is solved andorthogonality is guaranteed without an algorithm for preventingcollision between groups in hopping.

[0058] Moreover, because a specific value is selected for the detailedhopping and accordingly a relative hopping distance between groups hasrandomness, an ability of military operation is improved in anelectronic warfare.

[0059] As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. A frequency hopping sequence generator applied toa multi-group FH-FDMA, comprising: one binary sequence generator forgenerating consecutive binary sequences; and plural non-binary sequenceconverter for mapping a binary sequence into an independent non-binarysequence in each group by using a group ID.
 2. The generator of claim 1,wherein the non-binary sequence converter comprises: a shift registerblock for receiving a binary sequence; a group ID data storing unit forconverting the group ID into binary data; a divided band selector fordividing a hopping band as many as groups and allocating the groups toeach divided band; and a detailed hopping binary sequence selector foroutputting a value for generation of a detailed hopping sequence in eachdivided band.
 3. The generator of claim 2, wherein the divided bandselector comprises: an exclusive-OR operator for exclusive-ORing somebinary sequences outputted from the shift register block and binary dataof the group ID outputted from the group ID data storing unit, anddividing the hopping band
 4. The generator of claim 2, wherein thedetailed hopping binary sequence selector comprises: a decoder fordecoding the binary data of the group ID; and a calculating unit forperforming a logical operation on an output of the decoder and somebinary sequences outputted from the shift register block.